The yeast genome has been completed and the almost 6000 proteins from the yeast proteome are under analysis. This analysis will contribute to elucidate the basic mechanisms of unicellular eucaryotic life. Several aspects of such studies are relevant to human health problems. In particular, it should allow the development of new fungicides which would be more efficient and specific and would escape the complex multidrug cell export systems developed by pathogenic fungi. Also several human genes determining hereditary diseases have yeast homologues. The function of these homologues can be determined using a series of genetic tools which are unique to yeast. These human genes can also be expressed in yeast and be submitted to the same tools. Several examples of these approaches will be chosen concerning yeast homologues of human membrane proteins belonging to ion channels, permeases, cation transport-ATPases or ABC transporters superfamilies.